Azides triethylsilane

It should be remarked here that trimethylsilane 84 a or triethylsilane 84 b and most other known silanes, for example tetramethyldisiloxane 1788, are quite expensive for any large-scale reduction, whereas the subsequently described poly-methylhydrosiloxane 1856 (cf. reductions of an azide moiety in 1855 and a carbo-benzoxy moiety in 1859) is available as large-scale orders for ca 15 kg , which is only a fraction of the cost of any other silane. 

Sodium azide with alkynyl iodonium tosylates at — 70°C afforded an unstable ylide which in the presence of triethylsilane was transformed to different products, depending on the solvent [58] ... 

Again, no reaction was observed in the absence of mercaptoethanol. The mechanistic steps for the transformation were elucidated by the Chatgilialoglu et ah and are represented in Scheme 4.13, in analogy with the pathway reported for the radical reduction of aromatic azides with triethylsilane in toluene, with the addition of silyl radicals to the azide function, liberation of nitrogen and formation of silyl-substituted aminyl radical. The thiol is the hydrogen atom donor to this intermediate and it can be regenerated by its interaction with the silane, thus propagating the chain. The hydrolysis of the silylamine occurred... 

Benati, L. Bencivenni, G. Leardini, R. Minozzi, M. Nanni, D. Scialpi, R. Spagnolo, R Zanardi, G. Radical reduction of aromatic azides to amines with triethylsilane. J. Org. Ghent. 2006, 71, 5822-5825. 

Reductive cleavage (triethylsilane-trimethylsilyl triilate) of the isopropylidene derivatives 17 gives anhydro-sugars 18. The OH-2 groups in 18 have been further converted to mediates and displaced with purine bases or azide (further converted into a pyrimidine ring) to lead to nucleoside analogues. ... 

Reaction of (CH3)3CO- with triethylsilane and phenyl azide/ r-Butylbenzene... 

Reaction of the cyanohydrin mesylate 38 with azide (NaN3-CH2Cl2) led not to the product of simple displacement, but to the vinyl azide 40 in 30% yield, through the alkylidene carbene 39 (Scheme 7), which could be trapped by insertion into cyclohexene or triethylsilane. ... 

Finally, we examined the effect of varying the silane structure on reaction rate and selectivity. The use of tetramethyldisiloxane (TMDSO) (entry 5) showed a small but significant increase in the azide/alkane ratio (84 16 vs. 77 23 with ethanesulfonyl azide (7)). The reaction with poly(methylhydrosiloxane) (PMHS) was too slow (entry 6). However, addition of a sub-stoichiometric amount of phenylsilane was enough to give useful conversion (entry 7). Triethylsilane and triethoxysilane (entry 8 and 9) could not be used. Finally, combining tosyl azide (17) and TMDSO gave full conversion of 4-phenylbut-l-ene (3) in 3h with an improved azide/alkane ratio of 96 4 (entry 10) and 86% isolated yield. 

Spagnolo and co-workers discovered that thiols catalyze the reduction of azides in the presence of triethylsilane. Arylazides are reduced almost quantitatively to anilines (Scheme 8.44). Aliphatic azides were more reluctant to reduction. 

The quest for tin-free reductive methods led the same authors to develop the use of indium(lll) hydride ClalnH, generated in situ from triethylsilane and InCla. Aromatic and aliphatic azides as well as sulfonyl azides and acyl azides are reduced in moderate to excellent yield to the corresponding amines and amides. Azido nitriles are efficiently converted to the pyrrolidin-2-imines (Scheme 8.45). 

Recently, the photochemistry of azide 42 was studied by laser flash photolysis (Aex = 266nm) techniques in Fieon-113 (CF2CICFCI2) at room temperature. The formation of at least two intermediates, viz., triplet nitrene M3 (Aa,ax = 4(X)nm, lifetime 1.5 fis) and ethoxycarbonyl radical 44 (2 = 333 nm, lifetime 0.4/is), was observed (Scheme 11.22). The singlet nitrene M3 was deduced to have a lifetime between 2 and 10 ns in Freon-113 at ambient temperature. The kinetics of reactions of M3 with tetramethyleth-ylene and triethylsilane were also measured. ... 

---